Converting propylene in an oxygenate-contaminated propylene stream to non-polymerization derivative products

ABSTRACT

The invention provides for directing an oxygenate-contaminated propylene-containing stream derived from an oxygenate to olefin reaction system to a derivative non-polymerization reactor for conversion of the propylene to one or more derivative non-polymerization products. Exemplary derivative non-polymerization propylene conversion processes include: oxidation to form acrolein, oxidation to form acrylic acid, ammoxidation to form acrylonitrile, liquid phase oxidation to form acetone, liquid phase hydration to form isopropanol, hydroformylation to form n-butyraldehyde and its subsequent aldol/hydrogenation to form 2-ethylhexanol, direct or indirect oxidation to form propylene oxide, alkylation to form cumene in the presence of phosphoric acid/Kieselguhr or a zeolite and the subsequent selective hydroperoxidation of cumene to form acetone and phenol.

FIELD OF THE INVENTION

This invention relates to converting products of an oxygenate-to-olefinreaction system to non-polymerization products, and more particularly,to converting propylene in an oxygenate contaminatedpropylene-containing product stream from an oxygenate-to-olefin reactionsystem to one or more non-polymerization products.

BACKGROUND OF THE INVENTION

Light olefins, particularly ethylene and propylene, serve as feeds forthe production of numerous important chemicals and polymers. Olefinshave been traditionally produced from petroleum feedstock by catalyticor steam cracking processes. These cracking processes, especially steamcracking, produce light olefin(s) such as ethylene and/or propylene froma variety of hydrocarbon feedstock. Ethylene and propylene are importantcommodity petrochemicals useful in a variety of processes for makingplastics and other chemical compounds. Propylene is used to make variouspolypropylene plastics, and in making other chemicals such asacrylonitrile and propylene oxide. Because of the limited supply andescalating cost of petroleum feeds, the cost of producing olefins frompetroleum sources has increased steadily. Efforts to develop and improveolefin production technologies, particularly light olefins productiontechnologies, have increased.

The petrochemical industry has known for some time that oxygenates,especially alcohols, are convertible into light olefin(s). In anoxygenate to olefin (OTO) reaction system, a feedstock containing anoxygenate is vaporized and introduced into a reactor. Exemplaryoxygenates include alcohols such as methanol and ethanol, dimethylether, methyl ethyl ether, methyl formate, and dimethyl carbonate. In amethanol to olefin (MTO) reaction system, the oxygenate in theoxygenate-containing feedstock is methanol. In the reactor, the methanolcontacts a catalyst under conditions effective to create desirable lightolefins, such as propylene. Typically, molecular sieve catalysts havebeen used to convert oxygenate compounds to olefins.Silicoaluminophosphate (SAPO) molecular sieve catalysts are particularlydesirable in such conversion processes because they are highly selectivein the formation of ethylene and propylene.

Undesirable C₄+ or C₅+ olefins (heavy olefins) may be formed asbyproducts of the OTO process. U.S. Pat. No. 5,714,662 to Vora et al.provides a practical use for a C₃ and C₄ olefin stream separated from anMTO product effluent and for water byproduct formed in the MTO process.More specifically, the Vora et al. patent is directed to a process forproducing light olefins from crude methanol. The patent discloses thatpropylene and butylene fractions from the MTO product effluent may beconverted to high octane ether and other high value products.Optionally, butylene from the MTO process may be dimerized andhydrogenated to produce a C₈ alkylate having a high octane for use inblending motor gasoline.

Undesirable oxygenate compounds such as alcohols, aldehydes, ketones,esters, acids and ethers in the C₁ to C₆ range as well as tracequantities of aromatic compounds may also be formed in OTO reactors orin effluent processing. Additionally, a small amount of oxygenate fromthe feedstock, e.g., methanol or dimethyl ether (“DME”), may passthrough the OTO reactor with the product effluent without beingconverted to desired product. As a result of oxygenate synthesis and/orless than complete/quantitative conversion of the oxygenate feedstock inan OTO reaction system, the effluent from an OTO reactor may containundesirably high concentrations of oxygenate compounds.

Oxygenate and heavy olefin compounds contained in an OTO producteffluent may be undesirable for several reasons. For example, in orderfor an olefin-containing effluent to be suitable for catalyticpolymerization using a low valence state organometallic (e.g.,metallocene) and/or a Ziegler-Natta-type catalyst, the effluent shouldcontain no more than 1-5 ppm of oxygenates. Achieving these low levelsof oxygenates is possible using conventional separation technologies(i.e., fractionation, absorption and adsorption), thereby providing anolefin product stream of a sufficient grade for polymerization. However,increased investment and operating costs are required to separate andrecover the oxygenates from the desired polymerization quality lightolefins.

In a typical OTO reaction system, ethylene and propylene streams arereadily separable from one another and from a C₄+ product fractionthrough well known separation techniques. Although the ethylene fractionfrom an OTO reaction system is relatively pure with respect tooxygenates, a considerable amount of undesirable contaminants areconcentrated in the propylene product fraction. The major contaminantsin the propylene product fraction are oxygenates such as methanol,ethanol, dimethyl ether (DME), ethanal, propanal, acetone and isopropylalcohol. These oxygenates have proven expensive to remove from thepropylene product fraction. Thus, a need exists for providing end usesfor an oxygenate-contaminated propylene product fraction from an OTOreaction system without having to invest in removing the oxygenatecontaminants.

SUMMARY OF THE INVENTION

The present invention provides a practical use for apropylene-containing stream that contains a minor amount of oxygenatecontaminants. The invention is particularly suited for an unpurifiedpropylene stream or fraction from an oxygenate-to-olefin (OTO) reactionsystem, such as a methanol-to-olefin (MTO) reaction system. Applicantshave discovered that a variety of derivative non-polymerization reactionprocesses that require a propylene-containing feedstock are relativelyinsensitive to the presence of the specific oxygenate contaminants foundin an unpurified propylene-containing effluent that is derived from anOTO reaction system. Exemplary reaction processes that can tolerate morethan about 1 weight percent oxygenate contaminants in apropylene-containing feedstock include: oxidation to form acrolein,oxidation to form acrylic acid, ammoxidation to form acrylonitrile,liquid phase oxidation to form acetone, liquid phase hydration to formisopropanol, hydroformylation to form n-butyraldehyde and its subsequentaldol/hydrogenation to form 2-ethylhexanol, direct oxidation to formpropylene oxide, alkylation to form cumene in the presence of eitherzeolite or phosphoric acid/Kieselguhr catalysts, and the subsequentselective hydroperoxidation of cumene to form propylene oxide andphenol.

In one embodiment, the invention is directed to a process for forming aderivative product from an oxygenate-to-olefin (OTO) reaction systemproduct stream. This inventive process includes a step of providing aproduct stream from an OTO reaction system. The product stream comprisespropylene and one or more oxygenate contaminants such as, for example,methanol, ethanol, dimethyl ether (DME), ethanal, propanal, acetoneand/or isopropyl alcohol. The process includes directing the productstream to a derivative process reactor and converting the propylene inthe derivative process reactor to the derivative product. The derivativeproduct comprises one or more of acrolein, acrylic acid, acrylonitrile,acetone, isopropanol, cumene, n-butyraldehyde, iso-butyraldehyde,2-ethyl hexanol or propylene oxide. After the converting, a derivativeproduct effluent comprising the derivative product and at least aportion of the oxygenate contaminants is removed from the derivativeprocess reactor. Preferably, the oxygenate contaminant is removed fromthe derivative product effluent through distillation or other well-knownseparation techniques. The product stream optionally comprises at leastabout 1 wppm, at least about 10 wppm, at least about 1000 wppm, at leastabout 1 wt %, at least about 2 wt %, at least about 5 wt %, at leastabout 10 wt %, less than about 10 wt %, or from about 10 wppm to about10 wt % oxygenate contaminants, based on the total weight of the productstream.

Another embodiment of the invention provides a process for forming aproduct from a propylene-containing stream, including providing apropylene-containing stream from an oxygenate to olefin reaction system,and contacting propylene in the propylene-containing stream with acatalyst under conditions effective to form the product. Thepropylene-containing stream comprises at least about 1 wppm, at leastabout 10 wppm, at least about 1000 wppm, at least about 1 wt %, at leastabout 2 wt %, at least about 5 wt %, at least about 10 wt %, less thanabout 10 wt %, or from about 10 wppm to about 10 wt % oxygenatecontaminants, based on the total weight of the propylene-containingstream. The oxygenate contaminants comprise one or more of thefollowing: methanol, ethanol, dimethyl ether (DME), ethanal, propanal,acetone, isopropyl alcohol and/or a mixture thereof. A derivativeproduct effluent comprising the derivative product and the oxygenatecontaminant optionally is directed to a separation unit wherein at leasta portion of the oxygenate contaminants are removed from the derivativeproduct effluent.

Optionally, the product is selected from the group consisting ofacrolein, acrylic acid, acrylonitrile, acetone, isopropanol, cumene,n-butyraldehyde, iso-butyraldehyde, 2-ethyl hexanol, and propyleneoxide. Optionally, the product comprises acrolein, and the catalyst is acomplex oxide based upon molybdenum and bismuth in combination with oneor more of cobalt, iron, phosphorous or nickel. Alternatively, theproduct comprises acrylic acid, and the catalyst comprises an oxide of ametal selected from the group consisting of molybdenum, vanadiumoptionally with one or more of tungsten, copper, iron or manganese.Alternatively, the product comprises acrylonitrile, and the catalystcomprises an oxidic structure of the bismuth molybdate or bismuthferromolybdate types. Alternatively, the product comprises acetone, andthe catalyst comprises PdCl₂.CuCl.H₂0. Alternatively, the productcomprises isopropanol and the catalyst is selected from the groupconsisting of sodium silicotungstate, an ion exchange resin andsulphuric acid. Alternatively, the product comprises cumene and thecatalyst is selected from the group consisting of phosphoricacid/Kieselguhr or a zeolite. Alternatively, the product comprises2-ethylhexanol and the catalyst comprises a cobalt carbonyl salt, whichoptionally comprises a phosphine ligand complex. The phosphine ligandcomplex optionally comprises a rhodium phosphine ligand complex.Alternatively, the product comprises propylene oxide and the catalystcomprises a molybdenum complex in solution. The process optionallyfurther comprises the step of separating a majority of the oxygenatecontaminants from the product.

BRIEF DESCRIPTION OF THE DRAWING

This invention will be better understood by reference to the detaileddescription of the invention when taken together with the attacheddrawing, wherein:

FIG. 1 illustrates an oxygenate to olefin reaction system and a reactioneffluent separation system; and

FIG. 2 illustrates an oxygenate to olefin reaction system and a reactioneffluent separation system.

DETAILED DESCRIPTION OF THE INVENTION

Introduction

The present invention provides practical uses for propylene-containingstreams that contain minor amounts of oxygenate contaminants. Theinvention is particularly well-suited for an unpurified propylene streamderived from an oxygenate-to-olefin (OTO) reaction system and,particularly, from a methanol-to-olefin (MTO) reaction system. Since thepropylene-containing stream may contain a minor amount of oxygenatecontaminants, the product separation sequence in an OTO reaction systemcan be advantageously simplified, and a commensurate decrease instart-up and operating costs can be realized.

An unpurified propylene-containing stream derived from an OTO reactionsystem can, depending on reaction conditions and any upstream effluentprocessing, contain a minor amount of oxygenate contaminants such asmethanol, ethanol, dimethyl ether (DME), ethanal, propanal, acetone,isopropyl alcohol or a mixture thereof. It has now been discovered thatseveral non-polymerization derivative processes that requirepropylene-containing feedstocks are relatively insensitive to thepresence of these oxygenate contaminants. Specifically, the catalystsimplemented in these non-polymerization derivative reaction processesare relatively insensitive to the oxygenate contaminants contained in anunpurified propylene-containing fraction from an OTO reaction system. Asa result, an unpurified propylene-containing fraction from an OTOreaction system may be directed to a non-polymerization derivativereactor for conversion of the propylene contained therein to one or morenon-polymerization derivative products. As used herein, an “unpurified”or “contaminated” stream means a stream containing at least about 1wppm, optionally at least about 5 wppm, or optionally at least about 10wppm oxygenate contaminants, based on the total weight of the stream.

A non-limiting list of exemplary derivative non-polymerization propyleneconversion processes that can tolerate a propylene-containing feedstockcontaining a minor amount of oxygenate contaminants includes: oxidationto form acrolein, oxidation to form acrylic acid, ammoxidation to formacrylonitrile, liquid phase oxidation to form acetone, liquid phasehydration to form isopropanol, hydroformylation to form n-butyraldehydeand its subsequent aldol/hydrogenation to form 2-ethylhexanol, directoxidation to form propylene oxide, alkylation to form cumene in thepresence of either zeolite or phosphoric acid/Kieselguhr catalysts, andthe subsequent selective hydroperoxidation of cumene to form propyleneoxide and phenol. Thus, the unpurified propylene-containing fractionfrom an OTO reaction system is suitable for disposition to thesederivative non-polymerization processes. As a result, a significantcommercial savings can be realized by not having to yield a purifiedoxygenate-free stream from an OTO reaction system to a derivativenon-polymerization reaction unit. Each of these derivativenon-polymerization processes is discussed in more detail below after adetailed description of OTO Reaction systems.

Oxygenate to Olefin Reaction Systems

As indicated above, the present invention is particularly suited forconverting an unpurified propylene-containing stream from an OTOreaction system, which is discussed in more detail hereinafter, to oneor more derivative non-polymerization products.

Typically, molecular sieve catalysts have been used to convert oxygenatecompounds to light olefins. Silicoaluminophosphate (SAPO) molecularsieve catalysts are particularly desirable in such conversion processesbecause they are highly selective in the formation of ethylene andpropylene. A non-limiting list of preferable SAPO molecular sievecatalysts includes SAPO- 17, SAPO-18, SAPO-34, SAPO-35, SAPO-44, thesubstituted forms thereof, and mixtures thereof.

The feedstock preferably contains one or more aliphatic-containingcompounds that include alcohols, amines, carbonyl compounds for examplealdehydes, ketones and carboxylic acids, ethers, halides, mercaptans,sulfides, and the like, and mixtures thereof. The aliphatic moiety ofthe aliphatic-containing compounds typically contains from 1 to about 50carbon atoms, preferably from 1 to 20 carbon atoms, more preferably from1 to 10 carbon atoms, and more preferably from 1 to 4 carbon atoms, andmost preferably methanol.

Non-limiting examples of aliphatic-containing compounds include:alcohols such as methanol and ethanol, alkyl-mercaptans such as methylmercaptan and ethyl mercaptan, alkyl-sulfides such as methyl sulfide,alkyl-amines such as methyl amine, alkyl-ethers such as DME, diethylether and methylethyl ether, alkyl-halides such as methyl chloride andethyl chloride, alkyl ketones such as dimethyl ketone, alkyl-aldehydessuch as formaldehyde and acetaldehyde, and various acids such as aceticacid.

In a preferred embodiment, the feedstock contains one or moreoxygenates, more specifically, one or more organic compounds containingat least one oxygen atom. In a most preferred embodiment, the oxygenatein the feedstock is one or more alcohols, preferably aliphatic alcoholswhere the aliphatic moiety of the alcohol(s) has from 1 to 20 carbonatoms, preferably from 1 to 10 carbon atoms, and most preferably from 1to 4 carbon atoms. The alcohols useful as feedstock in the process ofthe invention include lower straight and branched chain aliphaticalcohols and their unsaturated counterparts. Non-limiting examples ofoxygenates include methanol, ethanol, n-propanol, isopropanol, methylethyl ether, DME, diethyl ether, di-isopropyl ether, formaldehyde,dimethyl carbonate, dimethyl ketone, acetic acid, and mixtures thereof.In the most preferred embodiment, the feedstock is selected from one ormore of methanol, ethanol, DME, diethyl ether or a combination thereof,more preferably methanol and DME, and most preferably methanol.

The various feedstocks discussed above, particularly a feedstockcontaining an oxygenate, more particularly a feedstock containing analcohol, is converted primarily into one or more olefins. The olefins orolefin monomers produced from the feedstock typically have from 2 to 30carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6carbon atoms, still more preferably 2 to 4 carbons atoms, and mostpreferably ethylene and/or propylene.

Non-limiting examples of olefin monomer(s) include ethylene, propylene,butene-1, pentene-1,4-methyl-pentene-1, hexene-1, octene-1 and decene-1,preferably ethylene, propylene, butene-1, pentene-1,4-methyl-pentene-1,hexene-1, octene-1 and isomers thereof. Other olefin monomers includeunsaturated monomers, diolefins having 4 to 18 carbon atoms, conjugatedor nonconjugated dienes, polyenes, vinyl monomers and cyclic olefins.

In the most preferred embodiment, the feedstock, preferably of one ormore oxygenates, is converted in the presence of a molecular sievecatalyst composition into olefin(s) having 2 to 6 carbons atoms,preferably 2 to 4 carbon atoms. Most preferably, the olefin(s), alone orcombination, are converted from a feedstock containing an oxygenate,preferably an alcohol, most preferably methanol, to the preferredolefin(s) ethylene and/or propylene.

The most preferred process is generally referred to as gas-to-olefins(GTO) or, alternatively, methanol-to-olefins (MTO). In an MTO process, amethanol-containing feedstock is converted in the presence of amolecular sieve catalyst composition into one or more olefins,preferably and predominantly, ethylene and/or propylene, referred toherein as light olefins. Preferably, at least 90 weight percent, morepreferably at least 95 weight percent, and most preferably at least 99weight percent of the methanol in the feedstock is converted to lightolefins, based on the total weight of the methanol in the feedstock.

The feedstock, in one embodiment, contains one or more diluents,typically used to reduce the concentration of the feedstock. Thediluents are generally non-reactive to the feedstock or molecular sievecatalyst composition. Non-limiting examples of diluents include helium,argon, nitrogen, carbon monoxide, carbon dioxide, water, essentiallynon-reactive paraffins (especially alkanes such as methane, ethane, andpropane), essentially non-reactive aromatic compounds, and mixturesthereof. The most preferred diluents are water and nitrogen, with waterbeing particularly preferred. In other embodiments, the feedstock doesnot contain any diluent.

The diluent may be used either in a liquid or a vapor form, or acombination thereof. The diluent is either added directly to a feedstockentering into a reactor or added directly into a reactor, or added witha molecular sieve catalyst composition. In one embodiment, the amount ofdiluent in the feedstock is in the range of from about 1 to about 99mole percent based on the total number of moles of the feedstock anddiluent, preferably from about 1 to 80 mole percent, more preferablyfrom about 5 to about 50, most preferably from about 5 to about 25. Inone embodiment, other hydrocarbons are added to a feedstock eitherdirectly or indirectly, and include olefin(s), paraffin(s), aromatic(s)(see for example U.S. Pat. No. 4,677,242, addition of aromatics) ormixtures thereof, preferably propylene, butylene, pentylene, and otherhydrocarbons having 4 or more carbon atoms, or mixtures thereof.

The process for converting a feedstock, especially a feedstockcontaining one or more oxygenates, in the presence of a molecular sievecatalyst composition of the invention, is carried out in a reactionprocess in a reactor, where the process is a fixed bed process, afluidized bed process (includes a turbulent bed process), preferably acontinuous fluidized bed process, and most preferably a continuous highvelocity fluidized bed process.

The reaction processes can take place in a variety of catalytic reactorssuch as hybrid reactors that have a dense bed or fixed bed reactionzones and/or fast fluidized bed reaction zones coupled together,circulating fluidized bed reactors, riser reactors, and the like.Suitable conventional reactor types are described in for example U.S.Pat. No. 4,076,796, U.S. Pat. No. 6,287,522 (dual riser), andFluidization Engineering, D. Kunii and O. Levenspiel, Robert E. KriegerPublishing Company, New York, N.Y. 1977, which are all herein fullyincorporated by reference.

The preferred reactor type is any of the riser reactors generallydescribed in Riser Reactor, Fluidization and Fluid-Particle Systems,pages 48 to 59, F. A. Zenz and D. F. Othmer, Reinhold PublishingCorporation, New York, 1960, and U.S. Pat. No. 6,166,282 (fast-fluidizedbed reactor), and U.S. patent application Ser. No. 09/564,613 filed May4, 2000 (multiple riser reactor), which are all herein fullyincorporated by reference.

In an embodiment, the amount of liquid feedstock fed separately orjointly with a vapor feedstock, to a reaction system is in the range offrom 0.1 weight percent to about 85 weight percent, preferably fromabout 1 weight percent to about 75 weight percent, more preferably fromabout 5 weight percent to about 65 weight percent based on the totalweight of the feedstock including any diluent contained therein. Theliquid and vapor feedstocks are preferably the same composition, orcontain varying proportions of the same or different feedstock with thesame or different diluent.

The conversion temperature employed in the conversion process,specifically within the reaction system, is in the range of from about392° F. (200° C.) to about 1832° F. (1000° C.), preferably from about482° F. (250° C.) to about 1472° F. (800° C.), more preferably fromabout 482° F. (250° C.) to about 1382° F. (750° C.), yet more preferablyfrom about 572° F. (300° C.) to about 1202° F. (650° C.), yet even morepreferably from about 662° F. (350° C.) to about 1112° F. (600° C.) mostpreferably from about 662° F. (350° C.) to about 1022° F. (550° C.).

The conversion pressure employed in the conversion process, specificallywithin the reaction system, varies over a wide range includingautogenous pressure. The conversion pressure is based on the partialpressure of the feedstock exclusive of any diluent therein. Typicallythe conversion pressure employed in the process is in the range of fromabout 0.1 kPaa to about 5 MPaa, preferably from about 5 kPaa to about 1MPaa, and most preferably from about 20 kPaa to about 500 kPaa.

The weight hourly space velocity (WHSV), particularly in a process forconverting a feedstock containing one or more oxygenates in the presenceof a molecular sieve catalyst composition within a reaction zone, isdefined as the total weight of the feedstock excluding any diluents fedto the reaction zone per hour per weight of molecular sieve in themolecular sieve catalyst composition in the reaction zone. The WHSV ismaintained at a level sufficient to keep the catalyst composition in afluidized state within a reactor.

Typically, the WHSV ranges from about 1 hr⁻¹ to about 5000 hr⁻¹,preferably from about 2 hr⁻¹ to about 3000 hr⁻¹, more preferably fromabout 5 hr⁻¹ to about 1500 hr⁻¹, and most preferably from about 10 hr⁻¹to about 1000 hr⁻¹. In one preferred embodiment, the WHSV is greaterthan 20 hr⁻¹, preferably the WHSV for conversion of a feedstockcontaining methanol, DME, or both, is in the range of from about 20 hr⁻¹to about 300 hr⁻¹.

The superficial gas velocity (SGV) of the feedstock including diluentand reaction products within the reaction system is preferablysufficient to fluidize the molecular sieve catalyst composition within areaction zone in the reactor. The SGV in the process, particularlywithin the reaction system, more particularly within the riserreactor(s), is at least 0.1 meter per second (m/sec), preferably greaterthan 0.5 m/sec, more preferably greater than 1 m/sec, even morepreferably greater than 2 m/sec, yet even more preferably greater than 3m/sec, and most preferably greater than 4 m/sec. See for example U.S.patent application Ser. No. 09/708,753 filed Nov. 8, 2000, which isherein incorporated by reference.

FIG. 1 is a flow diagram illustrating an OTO reaction system, generallydesignated 100, and will now be described in greater detail. Anoxygenate containing feedstock or feed stream 120 is fed to a feedvaporization and introduction (FVI) system 121, which subjects themethanol in the methanol-containing feed stream 120 to conditions, e.g.,heat and pressure, sufficient to at least partially vaporize themethanol. For example, the FVI system preferably includes a vapor-liquiddisengaging drum, in which conditions are sufficient to provide avaporized methanol-containing stream 122 and a liquid stream, not shown,which may include non-volatiles. The vaporized methanol-containingstream 122 is directed to OTO reactor unit 123, in which the methanol invaporized methanol-containing stream 122 contacts an OTO catalyst underconditions effective to convert at least a portion of the oxygenates tolight olefins in product stream 124. Product stream 124 includesmethane, ethylene, ethane, propylene, propane, C4 olefins, C5+hydrocarbons, other hydrocarbon components, water, and oxygenates suchas one or more of DME, methanol, ethanol, ethanal, propanal, acetone,and/or isopropyl alcohol.

The product stream 124 preferably is then directed to a quench unit 125,e.g., a quench tower, wherein the product stream 124 is cooled and waterand other readily condensable components are condensed. The condensedcomponents, which comprise a substantial amount of water, are withdrawnfrom the quench unit 125 through a quench bottoms stream 139. A portionof the condensed components are circulated through a recirculation line,not shown, back to the top of the quench unit 125. The recirculationline optionally contains a cooling unit, e.g., a heat exchanger, notshown, to further cool the condensed components so as to provide acooling medium, e.g., a quench medium, to further cool the components inquench unit 125.

Olefin vapor leaves through the overhead portion of quench unit 125through quench overhead line 126. The olefin vapor in quench overheadline 126 is compressed in one or more stages and one or more compressorsin compression zone 127 to form a compressed product stream 128. Aftereach of one or more stages, the compressed stream passes through a heatexchanger, not shown, and is cooled in order to condense out heaviercomponents such as residual water. The condensed component(s) arecollected in one or more knock out drums, not shown, between compressionstages and exit the compression zone 127 via compression condensatestream(s) 140. Compressed product stream 128 optionally passes through awater absorption unit, not shown, where methanol is preferably used asthe water absorbent. In the water absorption unit, the water absorbentcontacts the compressed product stream 128, preferably in acountercurrent manner, under conditions effective to separate water fromthe other components in the compressed product stream 128. The lightolefins are recovered from the water absorption unit in an overheadstream, not shown. Optionally-washed compressed product stream 128 isdirected to a separation system for separating the various componentscontained therein.

A variety of separation systems may be implemented in accordance withthe present invention so long as the separation system forms apropylene-containing stream suitable for conversion to the one or morenon-polymerization derivative products disclosed herein. U.S. patentapplication Ser. No. 10/125,138, filed Apr. 18, 2002, and Ser. No.10/124,859, also filed Apr. 18, 2002, the entireties of which areincorporated herein by reference, describe two separation schemes whichmay be implemented in accordance with the present invention. Twoadditional separation systems that may form the contaminatedpropylene-containing stream for use in the non-polymerization derivativeprocesses are described in U.S. patent application Ser. No. 10/383,204,which was filed Mar. 6, 2003, and in U.S. patent application Ser. No.10/635,410 (methanol/water wash to remove some oxygenates), which wasfiled on Aug. 6, 2003, the entireties of which are incorporated hereinby reference. One exemplary non-limiting separation system isillustrated in FIG. 1.

As shown, compressed product stream 128 is directed to a C3− separationzone 129. Compressed product stream 128 may include methanol, ethanol,DME, ethanal, propanal, acetone, isopropyl alcohol or a mixture thereof,in addition to ethane, ethylene and propylene. The C3− separation zone129 separates ethylene and propylene, as well as lighter components,from at least some of the DME and heavier components, including C4olefins, C5+ hydrocarbons, unreacted methanol, and methanol remainingfrom the optional water absorption unit. The C3− separation zone 129includes one or more separation units, e.g., distillation columns, whichare adapted to separate C3− components from some of the DME and heaviercomponents. Additional methanol, not shown, optionally is added to theC3− separation zone 129 to reduce hydrate and/or free water formation. Amajority of the ethylene and propylene from compressed product stream128 exits the C3− separation zone 129 via C3− overhead stream 130. Someof the DME and heavier components, which include C4+ olefins and C5+hydrocarbons, exits the C3− separation zone 129 through C4+ bottomsstream 141.

The C3− components in C3− overhead stream 130 preferably are directed toa caustic wash unit 131, in which the C3− overhead stream 130 contacts acaustic wash medium under conditions effective to remove carbon dioxideand carbonic acid therefrom and form CO₂ depleted stream 132.Preferably, the caustic wash medium is sent through a line, not shown,to the top portion of the caustic wash unit 131 to remove carbondioxide, which is entrained in the C3− overhead stream 130. Spentcaustic leaves the caustic wash unit 131 through a waste caustic line,not shown.

Caustic treated ethylene and propylene exits caustic wash unit 131through CO₂ depleted stream 132 and preferably is directed to a waterwash column, not shown, and/or to drying section 133. Water enters theoptional water wash column and water and absorbed components exit thewater wash column through a bottoms line, not shown. Water washedethylene and propylene exit the water wash column through an overheadline, not shown, and pass through a drying section 133. Dry productstream 134 optionally contains less than 5 weight percent water, lessthan 1 weight percent water, or less than 0.5 weight percent water,based on the total weight of the dry methanol stream 134. Dry productstream 134 exits the drying section 133 and is directed to a C2/C3separation system 135.

In one embodiment of this invention, separation is by conventionaldistillation. Distillation is carried out using a vessel or tower havinginternal packing or trays that creates a temperature difference from topto bottom of the tower. The upper portion of the tower is the coolerportion, and higher volatile components in the feed exit from the top ofthe tower. C2/C3 separation system 135 preferably includes one or morecryogenic fractionation columns. The C2/C3 separation system 135preferably forms a tail gas stream 136, an ethylene product stream 137,and a propylene product stream 138. Optionally, the tail gas stream 136is first removed from the C2+ components in dry product stream 134, andC2 components are then separated from C3 components. Alternatively, theC3 components are removed from the C2− components (including the lightends, which form the tail gas) in a first separation step followed bytail gas separation from the C2 components in a second step.

The tail gas stream 136 preferably includes the majority of the methaneand hydrogen that was present in the dry product stream 134; theethylene product stream 137 preferably includes a majority of theethylene that was present in the dry product stream 134; and thepropylene product stream 138 preferably includes a majority of thepropylene that was present in the dry product stream. The ethyleneproduct stream 137 preferably is used as a monomer for the formation ofpolyethylene. The tail gas stream 136 optionally is burned as a fuel inone or more of the steps of the OTO reaction process.

According to the present invention, the C2/C3 separation system 135 isdesigned so that propylene product stream 138 contains one or moreoxygenate contaminants. At least a portion of the propylene productstream 138 preferably is directed to one or more derivativenon-polymerization reactor units for conversion of the propylene to oneor more derivative non-polymer products.

The oxygenate contaminant optionally is selected from one or more ofmethanol, ethanol, dimethyl ether (DME), ethanal, propylene, acetone,isopropyl alcohol or a mixture thereof. The propylene product stream 138optionally comprises at least about 1 wppm, at least about 5 wppm, atleast about 10 wppm, at least about 1000 wppm, at least about 1 weightpercent, at least about 2 weight percent, or at least about 5 weightpercent oxygenate contaminants, based on the total weight of thepropylene product stream. Preferably, the propylene product stream 138comprises less than 10 weight percent oxygenate contaminants, based onthe total weight of the propylene product stream 138.

FIG. 2 illustrates a preferred separation system, which may beimplemented according to the present invention, and which provides apropylene-containing stream that may be suitable for disposition to oneor more non-polymerization derivative reaction processes according tothe present invention. As shown, an effluent stream 200 is provided,which contains ethane, ethylene, propane, propylene and a minor amountof one or more oxygenates such as methanol, ethanol, dimethyl ether(DME), ethanal, propanal, acetone, isopropyl alcohol and/or a mixturethereof. Preferably, the effluent stream 200 is derived from an OTOreaction system, not shown, and optionally has been quenched to remove asubstantial amount of water therefrom.

The effluent stream 200 is directed to first separation unit 201, whichpreferably is a wash column adapted to remove some of the non-DMEoxygenates from the initial effluent stream 200. A majority of the C4+hydrocarbon components preferably are removed, e.g., throughdistillation, from the effluent stream 200 prior to its introductioninto first separation unit 201. In the first separation unit 201, theeffluent stream 200 contacts an oxygenate removal medium 202, preferablymethanol, under conditions effective to remove some of the oxygenatestherefrom. This means that ethane, ethylene, propane, propylene and atleast some oxygenates are recoverable in a first overhead stream 203,with the bulk of the oxygenate removal medium 202, and some oxygenatesbeing recoverable in a first bottoms stream 204. The first overheadstream 203 also likely contains a minor amount of residual oxygenateremoval medium. The first separation unit 201 optionally includes areflux line and/or a reboiler line and corresponding heat exchangers,not shown, to facilitate separation of these components.

First overhead stream 203 is then directed to a second separation unit210, which preferably is a water wash column adapted to separate anyresidual oxygenate removal medium 202 carried over from the firstseparation unit 201 via first overhead stream 203. Specifically, insecond separation unit 210, the first overhead stream 203 contacts water209 under conditions effective to remove at least a majority of theresidual oxygenate removal medium therefrom. Thus, ethane, ethylene,propane, propylene and oxygenates from the first overhead stream 203 arerecoverable in a second overhead stream 211, with the bulk of theresidual oxygenate removal medium 202 and water 209 being recoverable ina second bottoms stream 218. The second separation unit 210 optionallyincludes a reflux line and/or a reboiler line and corresponding heatexchangers, not shown, to facilitate separation of these components.

Optionally, second overhead stream 211 is directed to a caustic washunit, not shown, to remove carbon dioxide, and/or a drying unit, notshown. Reverting to FIG. 2, second overhead stream 211 preferably isdirected to demethanizer feed train 212. Demethanizer feed train 212 isa “cold box” that preferably is formed of a series of coolers, e.g.,core exchangers, and knock out drums, not shown, that cool secondoverhead stream 211 and form a plurality of cooled streams 214A-C.Cooled streams 214A-C may be in liquid and/or vapor form. Preferably,cooled streams 214A-C are directed to a third separation unit 215 forfurther processing. The third separation unit 215 preferably is adistillation column adapted to separate light ends such as methane,hydrogen and/or carbon monoxide from ethane, ethylene, propane, DME andpropylene. Specifically, the third separation unit 215 separates thecooled streams 214A-C, collectively, into a third overhead stream 216,which contains a majority of the light ends that were present in thecooled streams 214A-C, and a third bottoms stream 217, which preferablycontains a majority of the ethane, ethylene, propane, oxygenates andpropylene that was present in the cooled streams 214A-C. The thirdseparation unit 215 optionally includes a reflux line and/or a reboilerline and corresponding heat exchangers, not shown, to facilitateseparation of the light ends from ethane, ethylene, propane, oxygenatesand propylene. Third overhead stream 216 optionally is used as a coolingmedium for cold box 212, and exits therefrom via tail gas stream 213.

Third bottoms stream 217 preferably is introduced into a fourthseparation unit 206. The fourth separation unit 206 preferably is adistillation column adapted to separate C2− components from C3+components. Specifically, the fourth separation unit 206 separates thethird bottoms stream 217 into a fourth overhead stream 207, whichcontains a majority of the ethane and ethylene that was present in thethird bottoms stream 217, and a fourth bottoms stream 208, whichpreferably contains a majority of the propane, oxygenates and propylenethat was present in the third bottoms stream 217. The fourth separationunit 206 optionally includes a reflux line and/or a reboiler line andcorresponding heat exchangers, not shown, to facilitate separation ofthe C2− components from the C3+ components. The fourth overhead stream207, optionally is directed to C2 splitter, not shown, for separation ofethane from ethylene.

If the effluent stream 200 was depleted in C4+ components, then thefourth bottoms stream 208 may, depending on the amount of propane andoxygenate contaminants in the effluent stream 300, contain mostlypropylene and a minor amount of oxygenate contaminants, and may bewell-suited for one or more derivative non-polymerization reactionprocesses according to the present invention. If higher qualitypropylene is desired, then the fourth bottoms stream 208 optionally isintroduced into fifth separation unit, not shown, for removal ofadditional propane and/or oxygenate components. The fifth separationunit preferably is a distillation column, e.g., a propane purge tower,adapted to separate propylene from propane and some oxygenates.

If the effluent stream 200 contains C4+ components in any appreciablequantity, then the process flow scheme according to the presentinvention preferably includes a depropanizer, not shown. Thedepropanizer is adapted to separate C4+ components from C3− components,e.g., light ends, ethylene, ethane, propylene, propane and DME. Theplacement of the depropanizer may vary widely. In the embodimentillustrated in FIG. 2, the depropanizer optionally receives and removesat least a majority of the C4+ components from one or more of thefollowing streams: the effluent stream 200, the second overhead stream211, the third bottoms stream 217 or the fourth bottoms stream 208.

If the effluent stream 200 contains acetylene, methyl acetylene,propadiene, or other multiply unsaturated components, then the system ofthe present invention preferably includes a hydrogenation converter,e.g., an acetylene or MAPD converter, not shown. If incorporated intothe present invention, the hydrogenation converter preferably receivesand processes one or more of the following streams: the second overheadstream 211, the third bottoms stream 217, the fourth overhead stream 207and/or the fourth bottoms stream 208. In the hydrogenation converter,acetylene contacts hydrogen and carbon dioxide under conditionseffective to convert at least a portion of the acetylene to ethylene.Similarly, methyl acetylene and/or propadiene contact hydrogen andcarbon dioxide under conditions effective to convert at least a portionof the methyl acetylene and/or propadiene to propylene. Components otherthan acetylene, methyl acetylene and propadiene that are present in theabove-identified streams preferably pass unaltered through thehydrogenation converter(s). The resulting acetylene-depleted streams arethen processed as described above with reference to FIG. 2.

Several non-polymerization derivative reaction processes according tothe present invention will now be disclosed in greater detail.

Ammoxidation of Propylene to Form Acrylonitrile

Acrylonitrile is the most-produced non-polymerization propylenederivative product. In the year 2000, 5.4 million tons of the world'spropylene, or about 10 percent, was used to synthesize acrylonitrile.Acrylonitrile is used virtually exclusively as an intermediate.Specifically, most of the acrylonitrile produced is used for acrylicfibers, ABS (acrylonitrile-butadiene-styrene) or SAN(styrene-acrylonitrile) copolymers for engineering plastic applications,adiponitrile (an intermediate for Nylon-66) or other nitrile-basedelastomers. The largest use of acrylonitrile is in the manufacture ofadiponitrile.

Acrylonitrile also polymerizes to form polyacrylonitrile or ORLON. Theinitiator for the polymerization typically is a mixture of ferroussulfate and hydrogen peroxide. These two compounds react to producehydroxyl radicals (□OH), which act as chain initiators.Polyacrylonitrile may be dissolved in N,N-dimethylformamide to form asolution that can be used to spin fibers. Fibers produced in thisprocess are used in making carpets and clothing.

Nearly all of the world's supply of acrylonitrile is produced by vaporphase ammoxidation of propylene. While not limiting the invention to aspecific derivative non-polymerization chemical reaction or reactionmechanism, the ammoxidation of propylene may be illustrated as follows:

The original well-known catalyst systems were based upon a bismuthphosphomolybdate (Bi, Mo, P) catalyst system as described in U.S. Pat.No. 2,904,580, the entirety of which is incorporated herein byreference. U.S. Pat. Nos. 3,230,246 and 3,658,877, the entireties ofwhich are incorporated herein by reference, show that this mixed oxidecatalyst system, while fairly highly selective toward the desiredacrylonitrile product, also exhibits considerable yields of acrolein.Subsequent advances in catalyst technology were aimed at improving theacrylonitrile yields and propylene utilizations. Catalyst compositionsemployed in this service comprise antimony-uranium (Sb-U) combinations,iron, or bismuth, molybdenum, and phosphorus (Fe, Bi, Mo, P)combinations, and in some instances copper, selenium or tellurium (Cu,Se, Te) are added as promoters, as described, for example, in U.S. Pat.Nos. 3,658,877; 4,156,660; 4,609,502; 4,618,593; 4,659,689; 4,424,141;4,316,856; 4,317,747; and 4,322,368, the entireties of which areincorporated herein by reference. Preferably, the catalyst is an oxidicstructure of the bismuth molybdate or bismuth ferromolybdate types,which are well-known in the art.

In one reaction process, chemical grade propylene, oxygen (as air), andammonia are catalytically converted to acrylonitrile using a fluidizedbed gas phase reactor. Typical operating temperatures are from about400° C. to about 500° C., more preferably from about 400° C. to about450° C., and pressures are from about 3 psig (20.7 kPag) and about 30psig (206.9 kpag). The acrylonitrile-containing reactor effluentpreferably is cooled and scrubbed with water in a counter-currentabsorber. The resulting aqueous solution contains the acrylonitrile andbyproducts. This aqueous solution is then purified in a series ofsubsequent separation units, e.g., fractionation columns, that produceboth crude acetonitrile, and fiber grade acrylonitrile as the majorproduct streams.

Typical byproducts from the propylene ammoxidation process includeacetonitrile, hydrogen cyanide, and carbon oxides (CO and CO₂). However,the product quality specifications for acrylonitrile also commonly listacetone, acetic acid, acetaldehyde (typically all in the 10-500 wppmrange) as possible contaminants. Thus, it has now been determined thatthe presence of one or more of these (or other) oxygenated hydrocarbonspecies in an OTO-derived propylene product stream is not significantlydetrimental to the conversion of the propylene in the propylene productstream to acrylonitrile. That is, the acrylonitrile synthesis process isamenable to converting an OTO-derived propylene feedstock that maycontain some level of these oxygenated contaminants to acrylonitrile.Accordingly, in one embodiment, the invention is directed to a processfor forming acrylonitrile. The process includes providing a productstream containing propylene and an oxygenate contaminant. Preferably,the product stream is derived from an OTO reaction system, and morepreferably from an MTO reaction system. The product stream is directedto an acrylonitrile derivative process reactor. In the acrylonitrilederivative process reactor, the propylene is converted to acrylonitrile.Preferably, the process includes contacting the propylene with ammonia,an oxygen-source, e.g., air, and a catalyst under conditions effectiveto form acrylonitrile. Preferably the catalyst is an oxidic structure ofthe bismuth molybdate or bismuth ferromolybdate types, which arewell-known in the art.

Additional descriptions of acrylonitrile synthesis processes andcatalysts used therein are described in Kirk Othmer Encyclopedia ofChemical Technology, 3rd edition, volume 1, pp. 414-426, and in Ullman'sEncyclopedia of Industrial Chemistry, 5th edition, volume A1, pp.177-184, the entireties of which are incorporated herein by reference,and in U.S. Pat. Nos. 2,904,580; 3,658,877; 4,156,660; 4,609,502;4,618,593; 4,659,689; 4,424,141; 4,316,856; 4,317,747; and 4,322,368,the entireties of which are incorporated herein by reference.

Synthesis of Adiponitrile from Acrylonitrile

As indicated above, the largest use of acrylonitrile is in themanufacture of adiponitrile. About one-third of the adiponitrile isformed by the electrohydrodimerization of acrylonitrile (the bulk of theremainder of adiponitrile is formed from the hydrocyanation ofbutadiene). Without limiting the invention to a particular mechanism,this reaction may be illustrated as follows:

Adiponitrile manufacture preferably is a head-to-head dimerization ofacrylonitrile. The reaction occurs in a two-phase system using a phasetransfer catalyst, well-known in the art. First, acrylonitrile isreduced to form a radical anion. Two radical anions couplesimultaneously with protonation to form a C6 chain. Hydrogen transferforms the final nitrile product. Thus, in one embodiment, the inventionis directed to converting acrylonitrile, which is produced from apropylene-containing stream from an OTO reaction system, toadiponitrile.

Optionally, the adipontrile formed from the OTO-derived propylene streamis hydrogenated to form hexamethylenediamine (HMDA), as is well-known tothose skilled in the art. This reaction is illustrated as follows:

In one embodiment, the present invention is directed to a process forforming a adiponitrile and/or HMDA. The process includes providing aproduct stream containing propylene and an oxygenate contaminant.Preferably, the product stream is derived from an OTO reaction system,and more preferably from an MTO reaction system. The product stream isdirected to an acrylonitrile derivative process reactor. In theacrylonitrile derivative process reactor, the propylene is converted toacrylonitrile. Preferably, the process includes contacting the propylenewith ammonia, an oxygen-source, e.g., air, and a catalyst underconditions effective to form acrylonitrile. Preferably the catalyst isan oxidic structure of the bismuth molybdate or bismuth ferromolybdatetypes, as is well-known in the art. The acrylonitrile is then optionallyisolated and directed to an adiponitrile reactor, which optionally isthe acrylonitrile derivative process reactor. In the adiponitrilereactor, the acrylonitrile contacts hydrogen and electrons from anelectron source under conditions effective to convert at least a portionof the acrylonitrile to adiponitrile. Optionally, the adiponitrile ishydrogenated to form HMDA. This hydrogenation process may occur in theacrylonitrile derivative process reactor, the adiponitrile reactor or ina third reaction vessel, e.g., an HMDA synthesis unit.

Direct and Indirect Oxidation of Propylene to Form Propylene Oxide

Like acrylonitrile, propylene oxide also is used primarily as anintermediate. The major dispositions for propylene oxide are to urethanepolyether polyols for foam applications, to propylene glycol and topolypropylene glycol. In the year 2000, 3.8 million tons of the world'spropylene, or about 7 percent, was used to synthesize propylene oxide.

Conventional conversion of propylene to propylene oxide production isbased upon the chlorohydrin process. In the first step of this process,gaseous propylene and chlorine are reacted in an aqueous solution toform a propylene-chloronium intermediate complex. Without limiting thepresent invention to a particular reaction or reaction mechanism, thisstep can be illustrated as follows:

The propylene-chloronium complex then reacts with water to formhydrochloric acid, and the propylene chlorohydrin isomers (PCH 1 & PCH2):

In the final epoxidation step, the aqueous chlorohydrin stream isreacted with a base (typically either calcium hydroxide, or sodiumhydroxide caustic), to form the propylene oxide product:

There are other variations of the chlorohydrin process that employalternate sources of chlorine, or electrochemical methods for producingpropylene oxide. Such processes are essentially the same chemistry bututilize the cell liquor from brine electrolysis cells.

Propylene oxide also may be formed through indirect oxidation ofpropylene. These indirect oxidation processes involve the use ofhydrogen peroxide as the oxygen source. However, the high cost ofhydrogen peroxide and the potential safety hazards associated with highconcentrations of the peroxide are key disadvantages of these processes.The oxidation of propylene with organic hydroperoxides in the presenceof catalysts now accounts for approximately half of the world'sproduction of propylene oxide. One of the most common examples of thisapproach begins with isobutane oxidation to form equimolar amounts oft-butyl hydroperoxide and t-butanol.

The t-butylhydroperoxide then reacts with the propylene to produce thepropylene oxide and additional t-butanol, as follows:

The presence of large concentrations of alcohols in the aqueous reactionmixture makes the indirect oxidation approach especially amenable toOTO-derived propylene streams that may contain concentrations ofresidual oxygenated byproducts.

Alternatively, ethylbenzene rather than isobutane is used for theinitial hydroperoxide formation. Propylene then is reacted with theethylbenzene hydroperoxide to form methyl benzyl alcohol (MBA) andpropylene oxide, as follows:

The MBA product optionally is dehydrated at high temperatures to formstyrene, as follows:

Styrene then can be polymerized through well-known techniques to formpolystyrene.

Historically, molybdenum salts have been used as the epoxidationcatalysts for the indirect oxidation of propylene to form propyleneoxide. Thus, in one embodiment of the present invention, the catalystimplemented in the derivative reactor is a molybdenum complex in aqueoussolution. More recently, however, titanium silicates or titaniumcontaining zeolites have been used for this purpose. A variety ofdifferent additives (for example cesium phosphate) can also be added tothe aqueous solution to stabilize the pH of the reaction medium.

The first step of the indirect oxidation process involves formation ofthe hydroperoxide. As shown above, the isobutane (for example) isreacted with oxygen to form the hydroperoxide. This reaction occurs attemperatures between 120-140° C., and pressures from about 25 bar toabout 35 bar. The crude peroxide stream is then passed to a series ofepoxidation reactors, where it is allowed to contact a titanium silicatecatalyst. Conditions in the epoxidation reactors get progressively moresevere as the catalyst ages in order to maximize conversion of thehydroperoxide. Common reaction conditions are 110° C. and 40 bar in thefirst reactor, and 120° C. in the subsequent reactor. Optionally, thepressure in the subsequent reactor is slightly lower than the pressurein the first reactor to allow the transfer of the contents between thereactors. The hydroperoxide selectivity to propylene oxide is about 80weight percent, reflecting decomposition of the peroxide to otherspecies (the crude peroxide stream contains small amounts of aldehydeand ketone byproducts).

The epoxidation reactor effluent is then subjected to a number ofpurification steps. Unreacted propylene preferably is recovered andrecycled in a first purification step. Subsequently, the propylene oxideproduct is recovered. The coproduct t-butanol preferably is recovered ina final purification step.

Additional descriptions of propylene oxide synthesis processes,catalysts implemented therein and product separation techniques aredescribed in Ullman's Encyclopedia of Industrial Chemistry, 5th edition,vol. A22, pp. 239-260, the entirety of which is incorporated herein byreference, in U.S. Pat. Nos. 3,458,534; 3,449,219; 3,360,584; and3,592,857, the entireties of which are incorporated herein by reference,and in United Kingdom Patents Nos. 1,261,617 and 1,339,296, which arealso incorporated herein by reference.

It has now been determined that the presence of one or more oxygenatedhydrocarbon species in an OTO-derived propylene product stream is notsignificantly detrimental to the conversion of the propylene in thepropylene product stream to propylene oxide, through either direct orindirect oxidation. That is, the propylene oxide synthesis processes areamenable to converting an OTO-derived propylene feedstock that maycontain some level of oxygenated contaminants to one or more ofpropylene oxide, propylene chlorohydrin, t-butanol, and/or MBA.

Accordingly, in one embodiment, the invention is directed to a processfor forming one or more of propylene oxide, propylene chlorohydrin,t-butanol, and/or MBA. The process includes providing a product streamcontaining propylene and an oxygenate contaminant. Preferably, theproduct stream is derived from an OTO reaction system, and morepreferably from an MTO reaction system. The product stream is directedto a propylene oxide derivative process reactor. In the propylene oxidederivative process reactor, the propylene is converted to one or more ofpropylene oxide, propylene chlorohydrin, t-butanol, and/or MBA.Optionally, the MBA is converted to styrene, and the styrene topolystyrene.

Propylene Hydroformylation to Form Butanals

In hydroformylation chemistry (sometimes referred to as Oxo chemistry),olefins are reacted with synthesis gas containing carbon monoxide andmolecular hydrogen to form aldehydes products having one additionalcarbon atom. These aldehyde products have utility as intermediates inthe manufacture of numerous commercially important chemicals. Thus, theinvention further provides processes in which hydroformylation isfollowed by reactions to produce such chemicals. For example, thealdehyde products formed through the oxo reaction optionally aredimerized through Aldol reaction processes to form larger aldehydes, asdiscussed in more detail below. The Aldol products optionally are thenhydrogenated to form one or more oxo alcohol products. Alternatively,the aldehyde products formed through the oxo reaction are hydrogenatedto oxo alcohols without first undergoing an Aldol reaction.

The aldehyde products of this invention will have especial value whenthe aldehydes are aldolized, hydrogenated to saturated oxo alcohols, andthe alcohols esterified, etherified or formed into acetals to giveplasticizers or synthetic lubricants. In the year 2000, 3.8 million tonsof the world's propylene, or about 7 percent, was used to synthesize oxoalcohols. Under circumstances where the olefin feed is ultimatelyderived from a low-value feedstock like natural gas, e.g., in caseswhere methane from natural gas is converted to methanol and the methanolto olefin, the products or product mixtures from aldolization andhydrogenation may have value as liquid transportable fuels, optionallyafter dehydration to the olefin, and if desired hydrogenation to aparaffin or paraffinic mixture.

Without limiting the present invention to a particular reaction orreaction mechanism, the hydroformylation of propylene can be illustratedas follows:

The hydroformylation reaction can be carried out using conventionalhydroformylation catalysts or catalyst precursors. The hydroformylationreaction involves contacting propylene, carbon monoxide and hydrogen inthe presence of a hydroformylation catalyst or precursor. Hydridotransition metal carbonyls having the general formula HM(CO)₄, where Mis Co, Rh, or Ru, are typical catalysts for this reaction. Rhodiumhydroformylation catalysts are particularly desirable in this inventionbecause they are particularly tolerant to the presence of oxygenatecontaminates that may be present in an OTO-derived propylene-containingstream. Suitable rhodium catalysts or catalyst precursors that can beimplemented in this invention include rhodium(II) and rhodium(III) saltssuch as rhodium(III) chloride, rhodium(III) nitrate, rhodium(III)sulfate, potassium rhodium sulfate (rhodium alum), rhodium(II) orrhodium(III) carboxylate, preferably rhodium(II) and rhodium(III)acetate, rhodium(III) oxide, salts of rhodic(III) acid, triammoniumhexachlororhodate (III).

Depending upon the catalyst used, the ratio of normal butyraldehyde toisobutyraldehyde produced can be controlled. The choice depends upon theultimate end use for the aldehydes. Several significant advances in thehydroformylation catalyst systems include incorporatingphosphorous-containing ligands, e.g., triphenylphosphine or phosphite,for improved performance.

In one embodiment of the invention, hydroformylation is carried outusing an oil-soluble rhodium complex comprising a low valence rhodium(Rh) complexed both with carbon monoxide and a triorganophosphoruscompound. The triorganophosphorus compound can include one or moreoil-soluble triarylphosphines, trialkylphosphines,alkyl-diaryl-phosphines, aryl-dialkylphosphines, triorganophosphites,particularly trialkylphosphites and triarylphosphites (in which listalkyl includes cycloalkyl), containing one or more phosphorus atoms permolecule capable of complexing with Rh by virtue of having a lone pairof electrons on the phosphorus.

In another embodiment, triorganophosphorus ligands can be used, whichpreferably have (a) a molar P:Rh ratio of at least about 2:1, (b) atotal concentration of phosphorus of at least about 0.01 mol/l; and (c)a [P]/Pco ratio maintained in the reactor of at least about 0.1mmol/l/kPa, where [P] is the total concentration of the phosphorus insolution, and Pco is the partial pressure of carbon monoxide in the gasphase.

Examples of triorganophosphorus ligands include trioctylphosphine,tricyclohexylphosphine, octyldiphenylphosphine,cyclohexyldiphenylphosphine, phenyldioctylphosphine,phenyldicyclohexylphosphine, triphenylphosphine, tri-p-tolylphosphine,trinaphthylphosphine, phenyl-dinaphthylphosphine,diphenylnaphthylphosphine, tri-(p-methoxyphenyl)phosphine,tri-(p-cyanophenyl)phosphine, tri-(p-nitrophenyl)phosphine, andp-N,N-dimethylaminophenyl(diphenyl)phosphine, trioctylphosphite ortri-p-tolylphosphite. An example of a bidentate compound which can beused is diphos-bis(diphenylphosphino)ethane.

Preferably, Rh concentration in the reaction mixture is in a range offrom about 1×10⁻⁵ to about 1×10⁻² moles/liter or, in effect, in a rangeof from about 1 to about 1000 ppm, preferably about 20 to about 500 ppm,based on the total weight of the solution.

Oxo chemistry is typically homogeneously catalyzed. Syngas and propyleneare fed to the hydroformylation reactor where the aldehyde is formed.The higher olefin catalyst is desirably contacted with the olefin feedstream in solution. The solution can comprise an oily solvent or amixture of such solvents. For example, aliphatic and aromatichydrocarbons (e.g., heptanes, cyclohexane, toluene), esters (e.g.,dioctyl phthalate), ethers, and polyethers (e.g., tetrahydrofuran, andtetraglyme), aldehydes (e.g., propanal, butanal) the condensationproducts of the oxo product aldehydes or the triorganophosphorus liganditself (e.g., triphenylphosphine).

Alternatively, as described in U.S. Pat. Nos. 4,248,802, 4,808,756,5,312,951 and 5,347,045, which are each incorporated herein byreference, the catalyst may contain a hydrophilic group. In such a case,an aqueous medium may be used.

Rhodium can be introduced into the reactor as a preformed catalyst, forexample, a solution of hydridocarbonyl tris(triphenylphosphine)rhodium(I); or it can be formed in situ. If the catalyst is formed insitu, the Rh may be introduced as a precursor such asacetylacetonatodicarbonyl rhodium(I) {Rh(CO)₂(acac)}, rhodium oxide{Rh₂O₃}, rhodium carbonyls {Rh₄(CO)₁₂, Rh₆(CO)₁₆}, tris(acetylacetonato) rhodium(I), {Rh(acac)₃}, or a triarylphosphine-substituted rhodium carbonyl {Rh(CO)₂(PAr₃)}₂, wherein Ar isan aryl group.

The hydroformylation reaction is run between about 40° C. and about 200°C., more preferably between about 90° C. and about 180° C., and morepreferably between about 110° C. and about 150° C. The reaction is alsodesirably carried out at a low pressure, e.g., a pressure of about 0.05to about 50 MPa (absolute), preferably about 0.1 to about 30 MPa, andmost preferably below about 5 MPa. It is particularly preferred thatcarbon monoxide partial pressure be not greater than about 50% of thetotal pressure. The proportions of carbon monoxide and hydrogen used inthe hydroformylation or oxo reactor at the foregoing pressures aredesirably maintained as follows: CO from about 1 to about 50 mol %,preferably about 1 to about 35 mol %; and H₂ from about 1 to about 98mol %, preferably about 10 to about 90 mol %.

The hydroformylation reaction can be conducted in a batch mode or,preferably, on a continuous basis. In a continuous mode, a residencetime of up to 4 hours can be used. If a plurality of reactors isemployed, a residence time as short as 1 minute can be employed.Otherwise a preferred residence time is in the range of from about ½ toabout 2 hours.

Since the hydroformylation process of the invention advantageously takesplace in the liquid phase and the reactants are gaseous compounds, ahigh contact surface area between the gas and liquid phases is desirableto avoid mass transfer limitations. A high contact surface area betweenthe catalyst solution and the gas phase can be obtained in a variety ofways. For example, by stirring in a batch autoclave operation. In acontinuous operation, the olefin feed stream can be contacted withcatalyst solution in, for example, a continuous-flow stirred autoclavewhere the feed is introduced and dispersed at the bottom of the vessel,preferably through a perforated inlet. Good contact between the catalystand the gas feed can also be ensured by dispersing a solution of thecatalyst on a high surface area support. Such a technique is commonlyreferred to as supported liquid phase catalysis. The catalyst can alsobe provided as part of a permeable gel.

The hydroformylation reaction can be performed in a single reactor.Examples of suitable reactors can be found in U.S. Pat. Nos. 4,287,369and 4,287,370 (Davy/UCC); U.S. Pat. No. 4,322,564 (Mitsubishi); U.S.Pat. No. 4,479,012 and EP-A-114,611 (both BASF); EP-A-103,810 andEP-A-144,745 (both Hoechst/Ruhrchemie). Two or more reactor vessels orreactor schemes configured in parallel can also be used. In addition, aplug flow reactor design, optionally with partial liquid productbackmixing, can give an efficient use of reactor volume.

It is preferred that the hydroformylation reaction be carried out morethan one reaction zone or vessel in series. Suitable reactorconfigurations are disclosed, for example, by Fowler et al in BritishPatent Specification No. 1,387,657, by Bunning et al. in U.S. Pat. No.4,593,127, by Miyazawa et al in U.S. Pat. No. 5,105,018, and by Unruh etal. in U.S. Pat. No. 5,367,106, the entireties of which are incorporatedherein by reference. Examples of individual hydroformylation reactorscan of the standard types described by Denbigh and Turner in “ChemicalReactor Theory” ISBN 0 521 07971 3, by Perry et al in “ChemicalEngineers' Handbook” ISBN 0-07-085547-1 or any more recent editions,e.g., a continuous stirred tank or a plug flow reactor with adequatecontact of the gas and the liquid flowing through the reactor.Advantageously these plug flow reactor designs or configurations includeways of partial backmixing of the reactor product liquid, as explained,for example, by Elliehausen et al in EP-A-3,985 and in DE 3,220,858.

Product selectivities range between 90-98 weight percent, with thebalance comprising byproducts, or secondary reaction products of thealdehydes themselves. These typically include C₄ alcohols, C₄ esters,aldehyde dimers, trimers, and condensation products. The presence oflarge concentrations of the oxygenates in the aqueous reaction mixturemakes the indirect oxidation approach especially amenable to OTO-derivedpropylene streams that may contain concentrations of residual oxygenatedbyproducts.

The reactor effluent preferably is flashed to separate the productaldehydes from the catalyst solution. Unreacted propylene and propaneare recovered from the product stream via distillation or otherseparation technique and recycled. The crude aldehyde product is furtherfractionated to recover both the normal-, and branched aldehydeproducts.

More especially, the invention provides a process for the manufacture ofbutanol, wherein the butenal formed by hydroformylation is hydrogenated;a process for the manufacture of butyric acid, wherein the aldehydeproduct is oxidized; a process for the manufacture of an aldol dimer ortrimer, wherein the aldehyde product is self-aldolized; a process forthe manufacture of a saturated aldehyde, wherein the aldol dimer ortrimer is hydrogenated to a corresponding saturated aldehyde; a processfor the manufacture of an unsaturated alcohol, wherein the aldol dimeror trimer is selectively hydrogenated; a process for the manufacture ofa saturated alcohol, wherein all double bonds in the aldol dimer ortrimer are hydrogenated; a process for the manufacture of a saturatedalcohol or acid, wherein the saturated aldehyde produced byhydrogenation of the aldol dimer or trimer is hydrogenated or oxidizedto form the corresponding saturated alcohol or acid; a process for themanufacture of an ester, wherein the saturated alcohol or the acid isesterified; a process for the manufacture of an aldol tetramer orpentamer, or mixtures thereof, by aldolization of the aldehyde mixturefrom hydroformylation; a process for the manufacture of a C₆ to C₂₀alcohol or alcohol mixture, wherein the aldol dimer, trimer, tetramer,pentamer, or mixture, is hydrogenated to the corresponding alcohol oralcohol mixture; a process for the manufacture of liquid olefin orolefin mixture, wherein the tetramer or pentamer alcohol is dehydrated;and a process for the manufacture of a liquid paraffin or paraffinmixtures, wherein the olefin mixture is hydrogenated.

Additional descriptions of hydroformylation processes and the catalystsimplemented therein are described in U.S. Pat. Nos. 6,274,756;6,030,930; 6,022,929; 5,675,041; 5,395,979; 5,382,701; 5,364,950;5,298,669; 5,288,918; 5,288,818; 4,835,299; 4,687,874; 4,668,651;4,642,388; 4,625,068; 4,599,206; 4,551,543; 4,528,404; 4,522,932;4,473,505; 4,419,195; 4,404,119; 4,400,299; and 4,268,682, theentireties of which are incorporated herein by reference.

The hydroformylation product n-butyraldehyde is particularly valuable.The largest commercial use for n-butyraldehyde is in its reduction toform n-butanol, through the following reaction:

Similarly, isobutyraldehyde optionally is reduced to isobutanol, asfollows:

In these reactions, n-butyraldehyde and isobutyraldehyde are reduced ton-butanol and isobutanol, respectively, by hydrogen and a metalcatalyst, by sodium in alcohol, and by lithium aluminum hydride. Thereducing agent preferably is sodium borohydride (NaBH₄) or nickel onmagenesia or copper chromite catalysts in fixed bed hydrogenationreactors with hydrogen at 140-200° C. and 12-20 bar pressure.

n-butanol can be subsequently converted through esterification to one ormore of butyl acetate, butyl acrylate and butyl methacrylate. Theseesters have uses as solvents for coatings. Thus, the present inventionis also directed to forming one of more of n-butanol, butyl acetate,butyl acrylate and butyl methacrylate from an OTO-derivedpropylene-containing feedstock.

If desired, the aldehydes formed in the hydroformylation process,described above, can undergo an Aldol addition to form longer chainunsaturated aldehydes (dimers). In this reaction, the aldehydes aresubjected to basic conditions, preferably about 3 weight percent causticsolution (NaOH), in a countercurrent wash column at 120-150° C. and 3-5bar. Optionally, the aldehydes formed in the Aldol addition reactionprocess undergo an Aldol condensation reaction process, wherein theAldol addition product is spontaneously converted to one or morepartially unsaturated aldehydes.

Without limiting the present invention, one Aldol addition reaction canbe illustrated as follows for the conversion of n-butyraldehyde to3-hydroxy-2-ethylhexanal:

For the Aldol addition conversion of iso-butyraldehyde to3-hydroxy-2,2,4-trimethylpentanal, the Aldol addition reaction can beillustrated as follows:

Optionally, the n-butyraldehyde reacts with iso-butyraldedyde in asimilar Aldol addition and/or condensation reaction process.

Optionally, the Aldol addition or condensation product or products aresubsequently reduced to one or more alcohols in a similar manner asshown above for n-butyraldehyde and isobutyrlaldehyde. For example,3-hydroxy-2-ethylhexanal, above, optionally is hydrogenated in thepresence of a catalyst, e.g., Co(PPh)₃.KOH, and Octanoic acid to form2-ethylhexanol. 3-hydroxy-2,2,4-trimethylpentanal optionally ishydrogenated to form 2,2,4-trimethylpentanol.

It has now been determined that the presence of one or more oxygenatedspecies in an OTO-derived propylene product stream is not significantlydetrimental to the conversion of the propylene in the propylene productstream to n-butyraldehyde and/or isobutyraldehyde throughhydroformylation. That is, the n-butyraldehyde and isobutyraldehydehydroformylation synthesis processes are amenable to converting anunpurified OTO-derived propylene feedstock that may contain some levelof oxygenated contaminants to n-butyraldehyde and isobutyraldehyde.

Accordingly, in one embodiment, the invention is directed to a processfor forming a n-butyraldehyde, and in another embodiment the inventionis directed to a process for forming isobutyraldehyde. The processesinclude providing a product stream containing propylene and an oxygenatecontaminant. Preferably, the product stream is derived from an OTOreaction system, and more preferably from an MTO reaction system. Theproduct stream is directed to a derivative process reactor. In thederivative process reactor, the propylene is converted ton-butyraldehyde and/or isobutyraldehyde. Optionally, the inventionincludes directing the n-butyraldehyde to a second derivativenon-polymerization reactor unit for converting the n-butyraldehyde to3-hydroxy-2-ethylhexanal through an Aldol addition reaction process.Similarly, in another embodiment, the invention optionally includesdirecting the isobutyraldehyde to a second derivative non-polymerizationreactor unit for converting the isobutyraldehyde to3-hydroxy-2,2,4-trimethylpentanal through an aldol addition reactionprocess. The inventive process optionally includes converting a mixtureof n-butyraldehyde and isobutyraldehyde, to 3-hydroxy-2-ethylhexanal and3-hydroxy-2,2,4-trimethylpentanal, respectively, in a single secondderivative non-polymerization reactor unit. In one embodiment, the aldoladdition or condensation product and/or the hydroformylation product(n-butyraldehyde and/or isobutyraldehyde) contacts hydrogen or ahydrogen-containing species in a hydrogenation unit under conditionseffective to at least partially reduce the aldol addition/condensationproduct and or the hydroformylation product, e.g., to a correspondingalcohol or corresponding aliphatic species.

Propylene Oxidation to Form Acetone

In another derivative non-polymerization reaction process according tothe present invention, propylene in a propylene-containing stream froman OTO reaction system is oxidized to form acetone. Acetone iscommercially valuable in the production of acetone cyanohydrin,Bisphenol A, and as a solvent. Without limiting the present invention toa specific reaction or reaction mechanism, the overall reactionstoichiometry for direct propylene oxidation to acetone is given by:

However, the above reaction is actually the end result of the followingelementary steps:

The catalyst for this process is an aqueous solution of a salt of aGroup VIII metal (particularly palladium or rhodium) in combination witha copper or iron salt, which is used to complete the oxidation/reductioncycle and preserve catalyst activity. As a result, propionaldehyde(propanal) is a major byproduct from this oxidation process. Othertypical oxygenated hydrocarbon byproducts from this process includeacetic acid, CO₂, propionic acid, and methyl acetate. Chlorinatedhydrocarbons are also formed in small quantities as byproducts of thisreaction. Also, since propylene is sparingly soluble in water, otheroxygenated hydrocarbons such as acetic acid, ethylene glycol, or dioxanecan be used to increase the miscibility of propylene in the catalystsolution.

Conceptually, the propylene oxidation process is similar to the ethyleneoxidation to acetaldehyde process via the Wacker process. The Wackerprocess is an industrial process for the manufacture of ethanal byoxidizing ethylene. For example, bubbling ethylene and oxygen whentreated by an acidified water solution of palladium and cupric chloridesyield acetaldehyde; reaction is catalyzed by PdCl₂—CuCl₂. During thereaction palladium forms a complex with ethylene, is reduced to Pd(0),and is then reoxidized by Cu(II). The process is run in one vessel at50-130° C. and at pressures of 3-10 atm (303-1013 kPa). Regeneration ofcupric chloride occurs in a separate oxidizer. The reactions are carriedout in two alternating steps: First, an oxygen source such as air isused to oxidize the catalyst into the +2 oxidation state. In the secondstep, the oxygen source is replaced by propylene, the palladium oxidizesthe propylene, and the palladium is re-oxidized by the excess of coppersalt in the solution. Typical reaction temperatures are between about110° C. and about 120° C. Higher temperatures favor the formation ofpropionaldehyde and other side reaction byproducts of acetone. Typicalreaction pressures are from about 5 atm (507 kPa) to about 12 atm (1216kPa), with higher pressures increasing the solubility of propylene inthe catalyst solution.

Additional descriptions of the oxidation of propylene to form acetoneand of the catalysts implemented in this process are in Ullman'sEncyclopedia of Industrial Chemistry, 5th edition, vol Al, pp. 79-96 andin U.S. Pat. No. 3,149,167 (1964), the entireties of which areincorporated herein by reference.

It has now been determined that the presence of one or more oxygenatedhydrocarbon species in an OTO-derived propylene product stream is notsignificantly detrimental to the conversion of the propylene in thepropylene product stream to acetone. That is, the acetone synthesisprocess is amenable to converting an unpurified OTO-derived propylenefeedstock that may contain some level of oxygenated contaminants toacetone. The process includes providing a product stream containingpropylene and an oxygenate contaminant. Preferably, the product streamis derived from an OTO reaction system, and more preferably from an MTOreaction system. The product stream is directed to an acetone derivativeprocess reactor. In the acetone derivative process reactor, thepropylene is converted to acetone. Optionally a catalyst is implementedin the conversion of propylene to acetone. Preferably, the catalystcomprises PdCl₂.CuCl.H₂O

Hydration of Propylene to Form Isopropyl Alcohol

The major chemical process for the formation of isopropyl alcohol is thehydration of propylene. In another derivative non-polymerizationreaction process according to the present invention, propylene in apropylene-containing stream from an OTO reaction system is hydrogenatedto form isopropyl alcohol. Isopropyl alcohol is used as an industrialand household solvent, in coatings and as metallic catalysts in paints,inks and coatings. In the year 2000, 1.9 million tons of the world'spropylene, or almost 4 percent, was used to synthesize isopropylalcohol.

The synthesis of isopropyl alcohol is a well-known two-step processwherein propylene is first dissolved in cold concentrated sulfuric acid.Propylene is able to dissolve in concentrated sulfuric acid because thepropylene reacts by addition to form an alkyl hydrogen sulfate. In thefirst step, propylene accepts a proton from sulfuric acid to form acarbocation, which reacts with a hydrogen sulfate ion to form an alkylhydrogen sulfate. In the second step, the alkyl hydrogen sulfate ishydrolyzed to isopropyl alcohol by heating the alkyl hydrogen sulfate inwater. The result of the addition of sulfuric acid to propylene followedby hydrolysis is a Markovnikov addition of —H and —OH. Without limitingthe invention to a particular mechanism, the overall reaction can beillustrated as follows:

The highly acidic environment of the first step in the above synthesisprocess makes the synthesis of isopropyl alcohol highly amenable forimplementing an unpurified propylene-containing stream from an OTOreaction system.

It has now been determined that the presence of one or more oxygenatedhydrocarbon species in an OTO-derived propylene product stream is notsignificantly detrimental to the conversion of the propylene in theOTO-derived propylene product stream to isopropyl alcohol. That is, theisopropyl alcohol synthesis process, discussed above, is amenable toconverting an unpurified OTO-derived propylene feedstock that maycontain some level of oxygenated contaminants to isopropyl alcohol. Theprocess includes providing a product stream containing propylene and anoxygenate contaminant. Preferably, the product stream is derived from anOTO reaction system, and more preferably from an MTO reaction system.The product stream is directed to an isopropyl alcohol derivativeprocess reactor. In the isopropyl alcohol derivative process reactor,the propylene is converted to isopropyl alcohol. In one embodiment, theinvention includes forming isopropyl hydrogen sulfate in a firstreaction step, which optionally occurs in a first derivative reactor,and then hydrolyzing the isopropyl hydrogen sulfate to form theisopropyl alcohol product, optionally in the first derivative reactor orin a second derivative reactor. Optionally, the formation of isopropylalcohol from propylene occurs in a single derivative reactor.

Oxidation of Propylene to Form Acrolein and Acrylic Acid

In another derivative non-polymerization reaction process according tothe present invention, propylene in a propylene-containing stream froman OTO reaction system is oxidized through catalytic vapor phaseoxidation to form acrolein and/or acrylic acid. Acrolein is used almostexclusively as the key intermediate in forming acrylic acid. Acrylicacid may be converted into acrylate esters (such as methyl methacrylate)or is polymerized to polyacrylic acid or other copolymer products. Inthe year 2000, 1.9 million tons of the world's propylene, or about 3.5percent, was used to synthesize acrylic acid.

In one embodiment of the present invention, propylene is oxidized toacrolein (2-propenal). While not limiting the invention to a particularreaction or reaction mechanism, the oxidation of propylene to acroleinmay be illustrated as follows:

The catalytic vapor phase oxidation of propylene to acrylic acid iscarried out in two steps. The first step is the catalytic vapor phaseoxidation of propylene to acrolein, shown above. The acrolein product isthen further oxidized to form acrylic acid, as follows:

Catalyst systems have also been developed that promote the directsynthesis of acrylic acid from propylene:

The major side reactions that occur in these reaction processes produceCO and CO₂. Acetic acid, formaldehyde, and/or acetaldehyde in minoramounts are also produced through side reactions. However, there arepathways that yield smaller amounts of oxygenates such as acetic acid,formaldehyde, and/or acetaldehyde.

The first commercial catalysts for propylene oxidation were based uponcopper oxide. These systems exhibited low propylene conversion activity,and low selectivity to acrolein. The subsequent use of bismuth molybdatecatalyst compositions improved selectivity to acrolein, but stillexhibited relatively low propylene conversion. Modern catalyst systemsare still based upon this bismuth molybdate system, although numerousadditional metals have been found to improve both activity andselectivity of the system. Common catalyst compositions for propyleneoxidation comprise one or more of Mo, Bi, Fe, Ni, P, Co, K, W, Si, Cr,and Sn. In addition, catalyst systems comprising B, Na, Mg, Tl, and Sm,have also been demonstrated. See, for example, U.S. Pat. No. 3,825,600(1974); U.S. Pat. No. 3,454,630 (1969); U.S. Pat. No. 3,778,386 (1973);U.S. Pat. No. 3,833,649 (1972); U.S. Pat. No. 4,008,280 (1972); FR Pat.No. 2,028,164; JP Pat. Nos. 32,048 (1972); 41,329; and 34,111 (1973); BEPat. No. 769,508 (1972); DE Pat. Nos. 2,165,335; 2,338,111 (1973);3,125,062; and 3,125,061 (1981); and EP Pat. No. 663 (1977), theentireties of which are all incorporated herein by reference. Typicaloperating conditions for these modem catalyst systems are in the rangeof from about 300° C. to about 355° C., and from about 150 kPa to about250 kPa reactor pressure. Contact times vary between about 1.5 to about3.5 seconds, and the propylene feed concentrations is in the range of5-8 molar percent. Propylene conversions are typically between 90-99+weight percent with these catalysts. Acrolein and acrylic acidselectivities are between 70-90 weight percent and 4-20 weight percent,respectively, with these systems.

Recent advances have shown alternative pathways to form acrolein frompropylene via thermal oxidation or photo-oxidation of propylene overzeolite catalysts. See, for example, U.S. Pat. Nos. 5,914,013; 5,827,406and 6,329,553, the entireties of which are incorporated herein byreference.

The single-step process for acrylic acid formation employs catalystsystems comparable to those described above, except that the principlecomponents are molybdenum oxide and tellurium oxide. The overall yieldof the single-step process is relatively low (50-60% maximum). Thus,most acrylic acid processes are based upon the two-step approach. Thefirst stage catalysts are selected from the acrolein-selective systemsdescribed above. Acrylic acid is produced at high selectivity in thesecond stage using catalysts comprising oxides of molybdenum andvanadium, promoted with other metals such as Al, Cu, W, Mn, Fe, Sb, Cr,Sr, or Ce. See, for example, U.S. Pat. Nos. 3,567,772; 3,644,509 and3,845,120; JP Pat. Nos. 26,287; 11,371 and 169; BE Pat. No. 698,273; GBPat. No. 1,267,189; DE Pat. Nos. 2,164,905; 2,413,206 and 2,152,037; FRPat. No. 2,032,915; and DE-OS Pat. No. 2,055,155, the entireties ofwhich are incorporated herein by reference.

The conversion and selectivity data for these catalyst systems clearlyshow that sum of the acrolein and acrylic acid selectivities are alwayslower than the overall propylene conversion. The difference betweenthese values represents the selectivity of the catalyst to otherbyproducts, e.g., CO, CO₂, or various oxygenated hydrocarbons.Typically, this difference is in the range of 2-5%. Thus, thesecatalysts, and this process should be amenable to a propylene feedstockcontaining oxygenates.

In acrolein and acrylic acid syntheses, liquid propylene (typicallychemical grade propylene containing 95 weight percent propylene and 5weight percent propane) is vaporized, mixed with air, and compressedbefore being diluted with about 250 psia (1724 kPaa) steam. The olefinfeed is preheated to about 400° F. (204° C.) before being introduced toa first oxidation reactor. Typical operating conditions in this reactorare 41 psia (283 kPaa). The reactor preferably is a shell and tubedesign, with molten salt on the shell side used as the cooling medium.The effluent gas from the first reactor is mixed with additional hot airand steam, heated to 460° F. (238° C.), and introduced to a secondreactor for further oxidation and form a second reactor effluent. Thesecond reactor effluent preferably is cooled, and directed to a quenchabsorber tower. Preferably, water is used in the quench column to absorbthe acrylic acid product, as well as unreacted acrolein, and othernon-volatile byproducts such as CO and CO₂. The bottoms streampreferably is passed to an azeotropic distillation column, wherein theacrylic acid is recovered from the other components in the bottomsstream. Typically, MIBK (methylisobutylketone) is used in this servicebecause it azeotropes with the water.

Additional descriptions of the oxidation of propylene to form acroleinand/or acrylic acid and of the catalysts implemented in this process aredescribed in Ullman's Encyclopedia of Industrial Chemistry, 5th edition,vol A1, pp. 149-176; Kirk Othmer Encyclopedia of Chemical Technology,3rd edition, vol 1., pp. 277-297; and in Kirk Othmer Encyclopedia ofChemical Technology, 4th edition, vol 1, pp. 232-250, the entireties ofwhich are incorporated herein by reference, as well as in U.S. Pat. Nos.3,825,600; 3,454,630; 3,778,386; 3,833,649; 4,008,280; 5,914,013;5,827,406; 6,329,553; 3,567,772; 3,644,509; and 3,845,120, theentireties of which are also incorporated herein by reference. Furtherdescriptions of these processes are also described in French PatentsNos. 2,028,164 and 2,032,915; German Patents Nos. 2,165,335; 3,125,061;3,125,062; 2,338,111; DE-OS 2,055,155; 2,152,037; 2,413,206 and2,164,905; Japan Patents Nos. 32,048; 41,329; 34,111; 26,287; and11,371; Great Britain Patent No. 1,267,189; Belgium Patents Nos. 769,508and 698,273; and EP Patent No. 663 (1977), the entireties of which areall incorporated herein by reference.

It has now been determined that the presence of one or more oxygenatedhydrocarbon species in an OTO-derived propylene product stream is notsignificantly detrimental to the conversion of the propylene in thepropylene product stream to acrolein and/or acrylic acid. That is, theacrolein and acrylic acid synthesis processes are amenable to convertingan unpurified OTO-derived propylene feedstock that may contain somelevel of oxygenated contaminants to these products. The process includesproviding a product stream containing propylene and an oxygenatecontaminant. Preferably, the product stream is derived from an OTOreaction system, and more preferably from an MTO reaction system. Theproduct stream is directed to a derivative process reactor. In thederivative process reactor, the propylene is converted to acrylic acidand/or acrolein. Optionally, the invention includes forming acrolein ina first reaction step, which may occur in a first derivative reactor,and then further oxidizing the acrolein to form the acrylic acidproduct, optionally in a second derivative reactor. Optionally, theformation of acrylic acid from propylene occurs in a single derivativereactor in a direct synthesis process, and optionally in a singleconversion process. In one embodiment, a catalyst is implemented in theconversion of propylene to acrolein and/or acrylic acid. Preferably, thecatalyst comprises a complex oxide based upon molybdenum and bismuth incombination with one or more of cobalt, iron phosphorous or nickel,particularly in the acrolein synthesis reaction. In another embodiment,particularly desirable in the synthesis of acrylic acid, the catalyst isan oxide of a metal selected from the group consisting of molybdenum,vanadium optionally with one or more of tungsten, copper, iron ormanganese.

Synthesis of Cumene from Propylene and Benzene

In another derivative non-polymerization reaction process according tothe present invention, propylene in a propylene-containing stream froman OTO reaction system is reacted with an acid and benzene to formcumene (isopropylbenzene). Cumene is an important intermediate in themanufacture of phenol and acetone, discussed below. In the year 2000,3.3 million tons of the world's propylene, or about 6 percent, was usedto synthesize cumene.

Specifically, propylene reacts with benzene in the presence of an acidvia a Friedel-Crafts alkylation mechanism to form the alkylbenzenecumene. Catalysts normally employed in new plants are zeolite-based,although older plants using aluminum chloride (AlCl₃) or phosphoric acidsupported on kieselguhr as catalyst are still operating. The reactionbegins with the addition of H⁺ to propylene to form a carbocation. Thecarbocation then acts as an electrophile in a second step and attacksthe benzene ring to form an arenium ion. The arenium ion then loses aproton to generate cumene. Without limiting the invention to aparticular reaction mechanism, the overall stoichiometry for thereaction of propylene with benzene to form cumene may be illustrated asfollows:

In one embodiment, propylene and benzene are brought into contact with acatalyst at high temperature and pressure in a fixed bed reactor.Various catalysts may be implemented in the alkylation of benzene toform cumene. The reaction is exothermic, and the reactor effluentoptionally is utilized as a heating agent to heat incoming feed(propylene and/or benzene). The benzene preferably is provided in excessto suppress dealkylation and side reactions. Ideally, the ratio ofbenzene to propylene in the reaction mixture is about 10:1.

Typically, the cumene process uses chemical grade propylene (nominally98% propylene), however, refinery grade propylene (nominally 70%propylene) can also be used. Oxygenate levels in chemical or refinerygrade propylene can range from as little as 10 wppm to as high asseveral wt %. As the cumene synthesis process occurs under highly acidicconditions, it has now been determined that the presence of one or moreof these (or other) oxygenated hydrocarbon species in an OTO-derivedpropylene product stream will not be significantly detrimental to theconversion of the propylene in the OTO-derived propylene product streamto cumene. That is, the cumene synthesis process is amenable toconverting an OTO-derived propylene feedstock that may contain somelevel of these oxygenated contaminants to cumene. Accordingly, in oneembodiment, the invention is directed to a process for forming cumene.The process includes providing a product stream containing propylene andan oxygenate contaminant. Preferably, the product stream is derived froman OTO reaction system, and more preferably from an MTO reaction system.The product stream is directed to a cumene derivative process reactor.In the cumene derivative process reactor, the propylene is reacted withbenzene to form cumene. Preferably, the process includes contacting thepropylene with benzene, over an acid catalyst, preferably a zeolite,AlCl₃, or solid phosphoric acid supported on kieselguhr, underconditions effective to form cumene.

Reaction of Cumene with Oxygen to Form Acetone and Phenol

According to one embodiment of the present invention, cumene formed froma propylene-containing stream derived from an OTO reaction system isconverted to phenol and acetone. Phenol is a very important article ofcommerce. Worldwide production is more than 3 million tons per year.Phenol is a starting material for the production of phenol-formaldehyderesins, which are polymers that have a variety of uses, includingplywood adhesives, glass fiber (Fiberglass) insulation, and moldedphenolic plastics used in automobiles and appliances. Acetone iscommercially valuable in the production of acetone cyanohydrin,Bisphenol A, methyl methacrylate, poly(methyl methacrylate) and as asolvent. The formation of phenol preferably occurs in a two stepprocess. In the first step, cumene undergoes an autoxidation reactionwith molecular oxygen. The oxidation of cumene preferably occurs at atemperature between about 95° C. and about 135° C. Overall, the firststep can be illustrated as follows:

This reaction is a free-radical chain reaction. Oxygen initiates thereaction because it is a double free radical or diradical. In theinitiation step, oxygen abstracts a hydrogen atom from cumene to give aresonance-stabilized benzylic free radical. Cumene hydroperoxide isformed in the subsequent propagation steps of the reaction. The cumenehydroperoxide then undergoes a rearrangement under acidic conditions toform phenol and acetone, as follows:

Preferably, the cumene hydroperoxide is treated with sulfuric acid,preferably with an about 5 to about 25 weight percent sulfuric acidsolution, more preferably with an about 10 percent sulfuric acidsolution. The rearrangement involves protonation of cumene hydroperoxidefollowed by loss of water to give an ion with an electron-deficientoxygen. This cation spontaneously rearranges to a more stablecarbocation. The carbocation reacts with water to give form a hemiacetalthat is unstable and breaks down spontaneously to form the phenol andthe acetone.

The reaction of cumene to acetone and/or phenol preferably occurs in aphenol/acetone synthesis unit. The first and second steps, illustratedand described above optionally both occur in the phenol/acetonesynthesis unit or in separate reaction vessels.

Ideally, the acetone and phenol formed in the above reaction, inaddition to any side reaction products, are separated in one or moreseparation units, e.g., distillation columns, extraction units and/orwashing column. Exemplary side reaction products include acetophenone,2-phenylpropan-2-ol and α-methylstyrene. Preferably, any α-methylstyreneproduced is separated by vacuum distillation and hydrogenated back tocumene for recycle to the phenol/acetone synthesis unit.

In one embodiment of the present invention, cumene formed fromOTO-derived propylene is converted to phenol and/or acetone. The processincludes providing a product stream containing propylene and anoxygenate contaminant. Preferably, the product stream is derived from anOTO reaction system, and more preferably from an MTO reaction system.The product stream is directed to a cumene derivative process reactor.In the cumene derivative process reactor, the propylene is converted tocumene. Preferably, the process includes contacting the propylene withan acid, preferably AlCl₃/HCl, sulfuric acid or hydrofluoric acid, underconditions effective to form cumene. The cumene then contacts an oxygensource, preferably molecular oxygen, under conditions effective toconvert at least a portion of the cumene to cumene hydroperoxide. Thisconversion step optionally occurs in the cumene derivative processreactor or a separate cumene hydroperoxide synthesis unit. The cumenehydroperoxide preferably is directed to a phenol/acetone synthesis unit,which optionally is the same unit as the cumene derivative processreactor, the cumene hydroperoxide synthesis unit, or a third separateand independent synthesis unit. In the phenol/acetone synthesis unit,the cumene hydroperoxide preferably contacts an acid, preferably a 5-25%sulfuric acid solution, under conditions effective to convert at least aportion of the cumene hydroperoxide to one or both of phenol andacetone. Preferably, both phenol and acetone are produce andsubsequently separated in a separation unit, e.g., a distillationcolumn.

Syntheses of Acetone Cyanohydrin and Methyl Methacrylate from Acetone

As indicated above, acetone is commercially valuable in the productionof acetone cyanohydrin, Bisphenol A, methyl methacrylate (MMA),poly(methyl methacrylate) (PMMA) and as a solvent. Accordingly, thepresent invention is also directed to the production of acetonecyanohydrin, Bisphenol A, MMA, and PMMA from an OTO-derivedpropylene-containing feedstock.

Acetone cyanohydrin is synthesized through the nucleophilic addition ofHCN to acetone in the presence of a base such as sodium hydroxide, asfollows:

Dehydration of the alcohol group of acetone cyanohydrin followed byesterification with methanol synthesizes methyl methacrylate (MMA).

MMA is an extremely valuable monomer for the production of PMMA (approx.1.2 billion pounds/year). PMMA is a high clarity resin used in glasssubstitutes.

Synthesis of Bisphenol A from Phenol and Acetone

Bisphenol A is manufactured from phenol and acetone. Bisphenol A isprimarily used in the production of polycarbonate and epoxy resins.Polycarbonates are used as glass substitutes in the automotive, compactdisc and eyeglass industries. Without limiting the invention to aparticular reaction mechanism, the reaction can be shown as follows:

The reaction preferably occurs at about 50° C. Typically, the reactiontakes from about 8 to about 23 hours for maximum conversion. Some ortho,para isomers are formed, however, most of the product is para, para.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, then, reference shouldbe made solely to the appended claims for purposes of determining thetrue scope of the present invention.

1. A process for forming a derivative product, the process comprisingthe steps of: (a) providing a product stream from an oxygenate-to-olefinreaction system, wherein the product stream contains propylene and oneor more oxygenate contaminants; (b) directing the product stream to aderivative process reactor; and (c) converting the propylene in thederivative process reactor to the derivative product, wherein thederivative product comprises one or more of acrolein, acrylic acid,acrylonitrile, acetone, isopropanol, cumene, n-butyraldehyde,iso-butyraldehyde, 2-ethylhexanol or propylene oxide.
 2. The process ofclaim 1, wherein the oxygenate contaminant comprises one or more ofmethanol, ethanol, dimethyl ether, ethanal, propanal, acetone, isopropylalcohol or mixtures thereof.
 3. The process of claim 1, wherein theproduct stream comprises at least about 10 wppm oxygenate contaminants,based on the total weight of the product stream.
 4. The process of claim3, wherein the product stream comprises at least about 1000 wppmoxygenate contaminants, based on the total weight of the product stream.5. The process of claim 4, wherein the product stream comprises at leastabout 1 weight percent oxygenate contaminants, based on the total weightof the product stream.
 6. The process of claim 5, wherein the productstream comprises at least about 2 weight percent oxygenate contaminants,based on the total weight of the product stream.
 7. The process of claim6, wherein the product stream comprises at least about 5 weight percentoxygenate contaminants, based on the total weight of the product stream.8. The process of claim 1, wherein the product stream comprises fromabout 10 wppm to about 10 weight percent oxygenate contaminants, basedon the total weight of the product stream.
 9. The process of claim 4,wherein the product stream comprises less than about 10 weight percentoxygenate contaminants, based on the total weight of the product stream.10. The process of claim 6, wherein the product stream comprises lessthan about 10 weight percent oxygenate contaminants, based on the totalweight of the product stream.
 11. The process of claim 7, wherein theproduct stream comprises less than about 10 weight percent oxygenatecontaminants, based on the total weight of the product stream.
 12. Aprocess for forming a product from a propylene-containing stream, theprocess comprising the steps of (a) providing a propylene-containingstream from an oxygenate-to-olefin reaction system; and (b) contactingpropylene in the propylene-containing stream with a catalyst underconditions effective to form the product, wherein thepropylene-containing stream comprises at least about 1 weight percent ofan oxygenate contaminant, wherein the oxygenate contaminant comprisesone or more of methanol, ethanol, dimethyl ether, ethanal, propanal,acetone, isopropyl alcohol or a mixture thereof, based on the totalweight of the propylene-containing stream.
 13. The process of claim 12,wherein the product is selected from the group consisting of acrolein,acrylic acid, acrylonitrile, acetone, isopropanol, cumene,n-butyraldehyde, iso-butyraldehyde, 2-ethyl hexanol, and propyleneoxide.
 14. The process of claim 12, wherein the product comprisesacrolein, and the catalyst comprises a complex oxide based uponmolybdenum and bismuth in combination with one or more of cobalt, iron,phosphorous or nickel.
 15. The process of claim 12, wherein the productcomprises acrylic acid, and the catalyst comprises an oxide of a metalselected from the group consisting of molybdenum, vanadium optionallywith one or more of tungsten, copper, iron or manganese.
 16. The processof claim 12, wherein the product comprises acrylonitrile, and thecatalyst comprises an oxidic structure of the bismuth molybdate orbismuth ferromolybdate types.
 17. The process of claim 12, wherein theproduct comprises acetone, and the catalyst comprises PdCl₂.CuCl.H₂0.18. The process of claim 12, wherein the product comprises isopropanoland the catalyst is selected from the group consisting of sodiumsilicotungstate, an ion exchange resin and sulphuric acid.
 19. Theprocess of claim 12, wherein the product comprises cumene and thecatalyst comprises phosphoric acid/Kieselguhr or a zeolite.
 20. Theprocess of claim 12, wherein the product comprises 2-ethylhexanol andthe catalyst comprises a cobalt carbonyl salt.
 21. The process of claim20, wherein the cobalt carbonyl salt comprises a phosphine ligandcomplex.
 22. The process of claim 21, wherein the phosphine ligandcomplex comprises a rhodium phosphine ligand complex.
 23. The process ofclaim 12, wherein the product comprises propylene oxide and the catalystcomprises a molybdenum complex in solution.
 24. The process of claim 12,wherein the propylene-containing stream comprises at least about 2weight percent oxygenate contaminants, based on the total weight of thepropylene-containing stream.
 25. The process of claim 12, wherein thepropylene-containing stream comprises at least about 5 weight percentoxygenate contaminants, based on the total weight of thepropylene-containing stream.
 26. The process of claim 12, wherein thepropylene-containing stream comprises at least about 10 weight percentoxygenate contaminants, based on the total weight of thepropylene-containing stream.
 27. The process of claim 12, wherein theprocess further comprises the step of separating a majority of theoxygenate contaminants from the product.